In the same way that you can schedule posts directly on the calendar, if you write a post and set a publication date on it, the post will automatically appear as scheduled on the calendar.
To schedule a post with a publication date, in the Status & Visibility box of the Document properties, click on immediately link next to Publish. There you can select the publication date and apply it.
Once you do that, you’ll see the post as scheduled in the editorial calendar of Nelio Content. Note that the calendar is completely synced with the WordPress post editor.